1. Technical Field
The present invention relates to a liquid ejection apparatus such as an ink jet type recording apparatus or the like and a control method thereof, in particular to a liquid ejection apparatus in which a liquid ejection head is moved with respect to a landing object while liquid is ejected from a nozzle and a control method thereof.
2. Related Art
A liquid ejection apparatus is an apparatus that includes an ejection head and in which all types of liquid are ejected from the ejection head. As the liquid ejection apparatus, for example, there is an image recording apparatus such as an ink jet type printer, an ink jet type plotter or the like. Furthermore, recently, characteristics in which an extremely small amount of liquid is exactly landed on a predetermined position, have been applied to various apparatuses. For example, it applies to a display manufacturing apparatus for manufacturing color filters of liquid crystal display or the like, an electrode forming apparatus for forming electrodes of an organic EL (Electro Luminescence) display and a FED (field emission display) or the like, and a chip manufacturing apparatus for manufacturing biochips (biochemical elements). Thus, liquid-phased ink is ejected at the recording head for image recording apparatus, and each of color material liquid of R (Red) G (Green) B (Blue) is ejected at a color material ejection head for a display manufacturing apparatus. In addition, liquid-phased electrode material is ejected at the electrode material ejection head for the electrode forming apparatus and liquid of a bioorganic substance is ejected at the bioorganic substance ejection head for the chip manufacturing apparatus.
In this type of liquid ejection apparatus, a pressure generation unit (for example, a piezoelectric transducer or a heating element) that is included in the liquid ejection head is driven to generate a drive signal that includes an ejection drive pulse that ejects liquid from a nozzle of the liquid ejection head or a fine vibration drive pulse that finely vibrates a meniscus at the nozzle. In addition, each of drive pulses that are included in the drive signal is selectively applied to a pressure generation unit so that ejection control or fine vibration control of liquid is performed. The above described drive signal is repeatedly generated according to a timing signal that is generated based on a position signal according to a reciprocating movement of the liquid ejection head, in other words, a movement position of the recording medium such as the recording paper (landing object of liquid). Accordingly, the liquid ejection may be synchronized with the moving of the main scanning direction of the liquid ejection head and accuracy of the landing position of liquid with respect to the recording medium may be increased. Generally, a generation period of the drive signal is set to a time corresponding to an ejection resolution (a recording resolution) with respect to the recording medium. For example, in a case of the printer, when one pixel is recorded, the time that corresponds to a movement distance of the recording head and the generation period of the drive signal are set to accord with each other.
In the above described liquid ejection apparatus, there is strong demand with respect to increasing the speed of the liquid ejection. Thus, it is required that a pressure generation unit (for example, a piezoelectric transducer or a heating element) that is included in the liquid ejection head is operated in a further short interval. Thus, it is required that the generation period of the drive signal is shortened. However, the above described fine vibration pulse is only for finely vibrating the meniscus and is not directly related to the ejection of liquid droplets. Thus, in a configuration where the fine vibration pulse is input per every generation period of the drive signal, the generation period of the drive signal is extended as much as the fine vibration pulse and an obstacle with respect to the increased speed of the liquid ejection occurs.
Regarding the above described problem, as is disclosed in JP-A-2004-299348, a liquid ejection apparatus is configured such that a drive signal is generated, in which a first drive signal (a first unit period signal) that includes both an ejection drive pulse and a fine vibration drive pulse, and a second drive signal (a second unit period signal) that is configured of only the ejection drive pulse without including the fine vibration drive pulse are mixed in one signal generation period that is defined as one timing signal. In other words, in the related art, the fine vibration drive pulse is generated whenever one drive signal is generated, while one fine vibration drive pulse is generated whenever two unit period signals are generated in the configuration of JP-A-2004-299348.
However, in a liquid ejection apparatus of the related art, acceleration or deceleration of the liquid ejection head is performed at a position that is outside of the lateral in a movement direction of a head from a liquid ejection area (in a case of a printer, a recording area of an image or the like) in a landing object. The liquid ejection is not performed at the acceleration or the deceleration area. In other words, the liquid ejection is performed only at the steady speed area of the liquid ejection head. Meanwhile, recently, since there is demand for improvement of a processing speed of the liquid ejection and a more compact size of the apparatus, a configuration is also employed in which the movement distance (a scanning distance) of the liquid ejection head is shortened, the acceleration and the deceleration (in other words, direction switchover operation) of the liquid ejection head is performed even on the liquid ejection area at the landing object, and the ejection is performed in the acceleration and the deceleration section. However, if ink is ejected in the acceleration and the deceleration area, since the movement speed of the liquid ejection head is slower compared to a steady speed period in which the movement speed of the liquid ejection head is constant, the landing position of the liquid may be biased at the landing object. Specifically, like the configuration that is disclosed in JP-A-2004-299348, in a configuration in which a plurality of unit period signals is included in one signal generation period that is defined as one timing signal, dots are formed on the landing object with substantially the same interval at the steady speed period while the forming position of the dots is biased on the landing object in the acceleration and the deceleration area. Accordingly, striping and uneven coloration may occur in the image that is recorded on the landing object such that there is a problem in that the image quality is decreased.